In this article we will cover:

  • What is Apple’s App Tracking Transparency (ATT) and Private Click Management (PCM)?
  • What tracking data from Facebook and Google Ads campaigns will be affected and what data will still be collected?
  • Changes required to your Facebook set-up
  • Impact of ATT on audiences and reported conversions
  • Impact on Google Analytics


Launch of Apple’s ATT

The launch of iOS 14.5 in spring 2021 was another step towards giving users greater control over their data privacy.

Apple requires all Apps on its App Store to agree to a new App Tracking Transparency (ATT) framework (if the App collects data about the end user).

Starting with the operating system iOS 14.5,  users will be asked (for any App that continues to request the IDFA from Apple), whether to allow an App to track the user’s activity across its and other companies’ Apps and websites.

If the user ‘Asks App not to Track’ then Apple will not disclose the IDFA (IDentifier For Advertisers) which is a unique device identifier.

Phone screen showing ATT pop-up asking to allow Facebook to track your activity across other companies' apps and websites

How Apple will provide feedback – Private Click Management (PCM)

Apple will use a new feature called Private Click Management (PCM) for measuring ad clicks across websites and from iOS Apps to websites. Learn more on the webkit site.

PCM allows only one piece of event data (a piece of event data could be a purchase, page view, download etc.) to be transferred to the ad provider (say Facebook Ads or Google Ads) and this one piece of data is sent randomly between 24 and 48 hours after the event (not 24-48 hours after the click on the ad).

This delay protects the user’s identity as it becomes much harder to link the click with the event.

Users on the Safari browser also have the option to opt-out of PCM.


Facebook’s response to ATT

Facebook will stop appending the fclid (Facebook click identifier) on clicks within an iOS App.

Facebook will use a system called Aggregated Event Management (AEM) that abides by the principles of Apple’s PCM (Private Click Management).

Prior to the implementation of ATT, Facebook allowed an almost unlimited number of events to be tracked on a website (such a product page view, add to cart, download, etc.)

Each and every time an event was triggered by a user on a website then the facebook pixel posted the event information to Facebook.

Limited to 8 events you can collect data on

With the introduction of Apple’s ATT framework, Facebook is now limiting accounts to only 8 events per domain.

(What is one domain? Well, and are treated as the same domain while and are treated as separate domains).

Facebook will automatically select the 8 events you are now limited to. But you can edit the selection in Events Manager. [If the account is new then you can create the 8 events].

Prioritise events – you only get one piece of event data per visit

You also need to prioritise these events from most important to least important.

The new process will only send one piece of event data per click from iOS14 devices that have asked Facebook not to track the App.

By setting the prioritization you can decide which piece of information to send.

Typically you want to know about the most valuable event on your site, such as a conversion for an e-commerce shop.

If the click doesn’t result in a conversion then the next most important event datum (as prioritized by you) is sent (which may be product view or add to cart).


How to still support ROAS bidding / Value Optimization

This one event datum causes a problem if you run your campaigns using Value Optimization (i.e. you are trying to optimize the value of conversions rather than just the number of conversions) as you need to know two pieces of information: was there a conversion and how much was it for?

Facebook has come up with a fix. They have moved Value Optimization to be managed in Events Manager. You will need to enable ‘Value Set’ in Events Manager.

If you enable Value Set then rather than having one event for conversion, Facebook automatically creates four conversion bands (value sets).

The four value sets might be: conversion with value between $0-$50; conversion with value $50-$100; conversion with value between $100-$200 and conversion with value >$200.

Now if someone converts then the single piece of data can be, for example ‘one conversion with value between $100 and $200’.

You don’t have to stick with just four bands – you can use all 8 of your events for value sets. This allows for more granular value buckets but means you will collect less data about user events where the user did not convert.

If you select a new event or change the prioritization then it will take three days before you can start optimizing to that event (as it may take 3 days to get initial data back: 24-hours for the event to be triggered after the click + up to 48 hours to be notified of the event after the event happened).

What to do now

  • Verify Domain – you must verify that you are the domain owner. Learn more on Facebook.
  • Decide on top 8 events – Facebook will make the initial decision but then you can edit.


Impact on how Facebook measures your campaign performance

Facebook has deprecated its 28-day click-through; 28-day view through and 7-day view-through windows.

The delivery attribution window (this is the attribution window you want to optimise performance by) will continue to be set at the Ad Set Level (e.g. optimize conversions based on 7-day click).

Previously, regardless of the delivery attribution window you had chosen to optimise the ad-set on, you could use the reporting tool to view, at an account level, the performance of the campaigns through different attribution windows.

Now on the reporting tool you will only be able to see performance through the same attribution window you have targeted.

Is the reporting data as accurate as it was?

The 1-day Click data will be modeled – a combination of actual conversions and estimate for conversions via iOS14.5 devices.

Facebook models the iOS 14.5 click through conversions not because it won’t ultimately know this number accurately (if you have set conversions as your top event priority) but because it takes up to 3 days to get the actual conversion data from Apple and the one piece of data received via AEM will be at the campaign level so an estimate for the split by Ad Set is also needed.

The 1-day view and 7-day click windows will be partial conversions (only people not on iOS14.5 or iOS 14.5 users that have asked to allow the App to Track).

Note – there still will be view-through conversions on devices where people have opted out of tracking but Facebook will not be told of them and has decided not to model these.

Table showing summary of change to Facebook conversion model with ATTimage source: Facebook seminar


ATT Impact on Facebook Targetting / Audiences

Facebook can see who has clicked on your ads but for people that have asked not to be tracked it doesn’t know if that individual made a conversion or viewed a product (if conversion is your top prioritized event it will know in aggregate how many conversions have been completed but not which individual users converted).

This means Facebook might include purchasers in audiences where you have asked to exclude them (such as exclude purchasers in remarketing campaigns or in prospecting campaigns).

It will also mean that it won’t be able to include people who have opted out of tracking in remarketing audiences based on events such as viewed a product.

Impact on Lookalike audiences

The accuracy of a ‘Lookalike Purchasers’ audience will diminish.

Facebook knows who has clicked on an ad, plus the identities of people who have allowed tracking and purchased.

For people who have opted out of tracking it will know who clicked but not which specific individuals have purchased (it will know the campaign) – so it will still have quite a lot of data to create a profile of a purchaser.


ATT Impact on Google Ads

The ATT impact for Google Ads is less than for Facebook because Google is less reliant on Apps.

The two major Google owned properties affected are the YouTube App and Google Maps App which were both using the IDFA.

Rather than have users of these apps be asked if they want to be tracked, Google has stopped requesting the IDFA.

Even without requesting the IDFA Google still needs to abide by other elements of ATT framework, so Google has also stopped appending the gclid (google click identifier) on clicks originating in these Apps.

Just as for the Facebook App, Google will not be able to track a conversion from a user who views a video ad in the YouTube mobile app and later converts in the mobile browser.

Google will model conversions (see below for more information).

Note, if the user in this example is signed in to their Google Account in the YouTube App and web browser then Google is permitted to track the conversion as the webkit guidelines state that:

‘We consider certain user actions, such as logging in to multiple first party websites or apps using the same account, to be implied consent to identifying the user as having the same identity in these multiple places. However, such logins should require a user action and be noticeable by the user, not be invisible or hidden.’

New Google Ads parameter = wbraid

A new parameter ‘wbraid’ will be used instead of gclid for clicks from iOS Apps (such as YouTube). The wbraid will not be unique to the user therefore preserving privacy but will contain some broad audience insights that are compliant with the ATT framework.


Google Ads – Modelled conversions

Google tracks ad clicks/interactions on their platforms and all conversions on your website – but cannot always see the journeys between the two events due to privacy constraints or technical limitations. Here are a couple of example where it loses visibility:

  • Clicks on the YouTube app on Apple/iOS devices where due to the ATT framework Google is no longer tracking that click.
  • Cross-channel conversions: When a user starts their journey on one device with an ad interaction, and completes the conversion on another.
  • A user has not permitted a cookie to be saved against their visit.
  • A user uses a browser such as Safari which allows cookies to last for only 7 days and a conversion happens after this timeframe.

in these cases, Google models conversions.

It uses the behaviours of users where conversions are observed (such as YouTube App clicks on Android and cross-channel conversions where users are signed into their Google Accounts across devices/browsers) to attribute conversions to interactions on its platforms where the conversion is not observed.

modelled conversions are reported with the same granularity as observed conversions.


ATT impact on app deep-link conversions

Some e-commerce stores use ‘deep links’ in their Google Ads – these links open the product page, for example, in the e-commerce store’s App (if the user has the App installed on their device) rather than in a web browser. When the App is on iOS then there will be reduced information collected about conversions.

For deep links it sounds like Google will use the wbraid parameter which complies with the ATT framework.


Impact of ATT on Google Ads remarketing campaigns, audience lists

Just as for Facebook, Google will lose some visibility on who has converted.

The accuracy of remarketing lists will drop.

make sure that you have ‘enhanced conversions‘ set-up which allows you to send hashed first-party, user-provided data from your website when a user converts. The data is then used to match your customers to Google accounts, which were signed-in to when they engaged with one of your ads.


Topics is a proposal in the Privacy Sandbox designed to preserve privacy while showing relevant content and ads.

Your browser will note the type of sites and content you visit and record that as a topic in your browser (one new topic per week, keeping three weeks’ of data – so always up to date).

These topics, saved in your browser, will determine the types of ads that you see – allowing an advertiser to target you with relevant ads without knowing details about you as an individual or sites that you have visited (thus preserving privacy).

You can manage the topics saved in your browser or turn-off this feature completely.


ATT Impact on Web Analytics, Google Analytics and UTM Parameters

UTM Parameters will still work (we think!) and if you have set up your Campaigns and Ad Sets to include UTM Parameters then you can can see via Google Analytics or your web analytics tool the number of last non-direct conversions by Campaign and Ad Set.

Google will not append gclid on Apple, and facebook will not append fclid for users that have asked not to be tracked, so that tracking information will be lost – it means that via Google Analytics or alternative web analytics tool you may see events of people that have asked not to be tracked (if you have UTM Parameters set up).

>>> Read our step-by-step guide to optimizing Google Ads


The interactive video below highlights some of the analyses we cover: